Mortality from ovarian cancer is estimated to be 14,000 annually, with lethality in over 75% of patients principally due to late diagnosis and peritoneal carcinomatosis. Knowledge of relevant ligand or receptor overexpression may be a prerequisite to effective diagnosis and clinical therapy, the latter as demonstrated by Herceptin treatment of breast carcinomas overexpressing HER-2/erbB-2. We have examined the expression, phosphorylation and Heregulin-induced activation of all four erbB receptors, as well as the effects of Heregulin (HRG) on the growth of five ovarian and three breast carcinoma cell lines. SK-OV3, NIH: OVCAR-3, NIH:OVCAR-8, Ovca 429 and Ovca 433 expressed all four receptors at variable levels by Western Blotting. However, erbB-3 was the only receptor that was constituitively phosphorylated (non-stimulated cells) in all five cell lines. These results are consistent with published data which demonstrate that the erbB-2/erbB-3 dimer is associated with the strongest signaling in the receptor homo- and heterodimeration heirarchy. Heregulin stimulation of these cell lines increased phosphorylation of only erbB-3 in NIH:OVCAR-8 and -3, and Ovca 429. SK-OV-3, the line which most highly over expresses erbB-2, and Ovca 433, which unlike the others is both non-clonogenic and non-tumorigenic, were unaffected. In receptor heterodimerization studies, erbB-3 and erbB-4 immunoprecipitation co-precipatated erbB-2 in all five lines. No ovarian carcinoma cell lines were growth-stimulated in monolayer or soft agar by HRG (up to 500ng/ml). However, HRG stimulated growth in monolayer and soft agar of all three breast lines examined. Hrg mRNA was not detectable in two of the three breast cancer cell lines examined. However, all five ovarian carcinoma lines expressed HRG mRNA by RT-PCR. These results, as suggested by the consistent expression of HRG mRNA and constituitve tyrosine phosphoylation of erbB-3 in all five ovarian lines, indicate endogenous production of HRG may account for their lack of a growth response to exogenous HRG. In constrast, exogenous HGR-induced proliferation in the breast lines SK-Br-3 and T47D may be due to their low or absent endogenous HRG production. These results were published in June, 1999: Pegues, JC, Kannan B, and Stromberg, K. ErbB receptor expression and growth response to Heregulin Beta-1 in five ovarian carcinoma cell lines. Int J Oncol 1999 Jun; 14 (6) 1169-1176. This Project Number, Z01 BL 03002-07, is now consolidated with Project Number Z01 BL 03001-08 to focus on angiogenesis-based gene expression in ovarian carcinomas.